Soybean seeds (cv. Giza 22) were treated with Bion, salicylic acid and saccharin as chemical inducers as well as Paenibacillus polymyxa and Pseudomonas fluorescens as biotic inducer to study their effect on the infection by Rhizoctonia solani under greenhouse and field conditions. Under greenhouse conditions, all treatments induced significant reduction in the percentages of pre- and postemergence damping-off compared to untreated (check) treatment. The highest survived plants was achieved 84% by the inducers Bion (3 mM) and salicylic acid (5 mM) 82% as compared to 90% by the fungicide Rizolex-T (3g/kg seeds) treatment which achieved. Significant increases in plant height and shoot dry weight of soybean plants were recorded with Bion and fungicide treatments followed by salicylic acid and P. polymyxa treatments compared with the check treatment. Under field conditions during 2013 and 2014 growing seasons, all treatments significantly reduced pre- and post-emergence damping-off and increased the percentage of survived plants compared with the check treatment at the two growing seasons. However, the highest survived plants (%) of the two seasons were
recorded in case of Rizolex-T (84.6%) and Bion (83.5%) followed by salicylic acid (77%) and P. polymyxa (76.2%) treatments compared with the check treatment (62.9%). Meantime, Bion, salicylic acid and P. polymyxa inducers significantly improved growth parameters, i.e. stem length, number of branches/plant, number of pods/plant and seeds weight/plant, compared to the check treatment throughout the two seasons. Also higher increase in seed yield (kg/feddan) was recorded throughout the two seasons by Bion and fungicide treatments (88.9% and 81.4 %, respectively), followed by salicylic acid and P. polymyxa (69.7% and 58.4%, respectively), compared to the check treatment. Concerning the plant enzyme activity, PO activity increased in Bion treatment by 64.1% followed by salicylic acid by 31.6%. Also, Bion treatment showed the highest increase (118%) in PPO activity over the check treatment. On the other hand, the content of total phenols increased in plants treated with different inducers, compared with untreated plants. The maximum increase (141.2%) in the content of phenolic compounds was recorded with Bion treatment over check treatment, followed by salicylic acid and P. polymyxa treatments (being 50% and 49.6%, respectively).